1. Field of the Art
This invention relates to a stretched blow molded vessel or stretched heat set blow molded vessel made from a linear polyarylenethioether having a melt viscosity of 3,000 to 20,000 poise, and also to a process for producing these stretched blow molded vessels.
2. Prior Art
Polyarylenethioethers, for example, poly-p-phenylenethioethers, have heat resistance which can stand the heat of steam sterilization and chemical resistance to strong acids, strong alkalis or various organic solvents, and therefore they have been expected to be useful as a material for vessels (bottles, tanks, flasks, etc.) for uses in medicine, foods and other various chemicals, if they can be molded into a shape of bottles. However, from the viewpoint of a molding material, polyarylenethioethers available in the prior art involve problems such that they are poor in linearity of the molecular structure, and therefore they can be formed into vessels with difficulty or, if forcibly made into shapes of bottles, they are too brittle to stand practical use.
On the other hand, from the viewpoint of processing techniques, there have been the problems such that (i) polyarylenethioethers have so great a crystallization rate that they can be molded into stretched bottles with extreme difficulty, or that (ii) according to the conventional extrusion blow molding, namely the process in which a parison is extruded and subjected to blow molding, drawdown of the parison takes place to a great degree and therefore molding into a vessel with a wall of a uniform cross section can be done with extreme difficulty.
For this reason, except for a multi-layer hollow vessel obtained by extrusion blow molding together with a crystalline polyolefin (Japanese Laid-Open Patent Publication No. 79233/1980), polyarylenethioethers have not generally been used alone as the resin for hollow vessels.